The present invention is directed to a threaded actuator for positioning a structure subjected to intense loads and forces, and particularly a motor driven extendible member positioned to receive and support an intense load.
In various systems, an extendible member is accurately located between a rest position and an operative position. In the operative position, an intense force and load may be placed on the member. A typical application developed by the assignee of the present invention relates to injection mold and die casting systems in which a core of a mold body is positioned between an opened and closed position. For example, in a side-action system for molding and casting apparatus, one or more cores are slidably mounted with respect to each other within the mold body to open and close the mold. Each movable core is similarly mounted within a slide cavity and coupled to a threaded actuator secured to the mold base. The threaded actuator includes an hydraulic cylinder unit including a threaded nose or portion from which the piston rod extends. The core slide is secured to the end of the rod and slidably mounted within the mold body. The threaded nose of the cylinder is positioned within a threaded flange secured to the base for accurate positioning of the cylinder and thereby the rod, slide and core with respect to its position by full or near extension of the cylinder unit. The cylinder unit is specially constructed with a high force locking system between the rod and cylinder such that with the core appropriately located, the core is held in place with an intense force often greater than the cylinder motive force and under a pre-loaded condition as a result of interconnection between the core slide and the mold body. Thus, the system is arranged with internal mating parts which develop a very large mechanical advantage in establishing high preload forces where desired or necessary.
The above system has been found to establish high quality parts having essentially zero flash and with minimal wear and maintenance costs in the side-action positioning to produce a highly cost effective system for molding and die casting when compared to other available system using toggle linkages, cam pins, heel blocks or other means for positioning of the cores. The system operation is dependent upon the accurate positioning of the threaded actuator and also in establishing high preloading on the supporting rod structure. Thus, although very rigid members are used for supporting of a core and in the core as such, it cannot be assumed under all conditions and particularly large intense forces, that even the large preload does not positively insure against some compression of the supporting structure during a molding cycle in the presence of the intense loading.
Although the threaded actuator has been operated very successfully in side action molding and die casting apparatus, accurate set up is required to establish the desired initial positioning of the threaded actuator as well as establishing and maintaining the desired preload on the slide system for each particular molding sequence or part formation. Recognizing that both of these factors are of significance in providing optimal constructions, continuous consideration for desired improvement in the positioning system is desirable in maintaining the high quality in the side-action systems.
The same desire for accurate positioning of motor-driven threaded actuators may of course arise in other applications and the present invention with its improvements can be readily applied to other motor-driven applications. The above described system includes a hydraulic cylinder as the motor means. In molds or other systems, motors may be used such as pneumatic, electric and mechanical motor devices including an extendible work member and a threaded connecting portion for positioning of the work member.